A microwave IC waveguide device module includes: a substrate having a throughhole; a microwave IC provided on or above the first face of the substrate; a waveguide member provided below the second face of the substrate opposite from the first face, the waveguide member having an electrically conductive waveguide face which opposes the throughhole; an electrically conductive member covering at least a portion of the second face that extends in a manner of following along the waveguide face; and an artificial magnetic conductor on both sides of the waveguide member. The substrate includes an inner-wall electrically conductive portion covering an inner wall of the throughhole and being electrically connected with the electrically conductive member. The signal terminal and the ground terminal of the IC are electrically connected respectively with two portions of the inner-wall electrically conductive portion opposing each other with the throughhole interposed therebetween.